For example, in a W-CDMA system, when a radio terminal comes near the border of an area that a base station as the move source (a base station which serves as the move source from the radio terminal starts moving), it detects a preamble signal sent from a base station as the move destination (a base station which serves as the move destination toward which the radio terminal moves). When the radio terminal comes near the boundary between the area that the base station as the move source covers and the area that the base station as the move destination covers, the preamble signal receiving sensitivity of the radio terminal is increased to a value higher than a threshold value and the radio terminal receives data sent from the both base stations in a synthesized form. Then, when the radio terminal enters the area that the base station as the move destination covers, the intensity of the preamble signal which is sent from the base station as the move source is decreased and the data signal sent from the base station as the move source is cut. As a result, it may become possible for the radio terminal to maintain communication even though the radio terminal moves striding over the boundary between two areas.
Incidentally, in mobile communication, a base station including a terminal-class-based handoff (handover) processing table in which whether handoff (handover) is possible is set per terminal class and a handoff control unit is proposed as disclosed, for example, in Japanese Laid-open Patent Publication No. 2000-184424. In the above mentioned base station, when it is detected that handoff is desirable from a quality information signal sent from a mobile terminal, the handoff control unit judges whether handoff is allowable with reference to the terminal-class-based handoff processing table using the terminal class of the mobile terminal. Then, only when handoff is judged to be allowable, handoff is executed.
However, in an existing system of the above mentioned type in which handoff is executed with reference to the terminal-class-based handoff processing table using the terminal class of the mobile terminal, for example, in the case that there exist many mobile terminals belonging to the same terminal class, many mobile terminals start gaining access to the base station as the move destination almost simultaneously when many users of the mobile terminals are on a train which is running at a high speed and when the train has passed through a tunnel and hence overcrowding may occur owing to concentrated accesses to the base station as the move destination.